Tough question....

You have several things mixed up, and I think it's best to separate them out.

CGI

Common Gateway Interface is a standard way that web servers can run programs, collecting input from web-forms, and returning results to the browser. It is slow but stable, and almost all servers support it. Most people use Perl when using CGI, but you do not have to, you can use virtually anything you want, e.g. BASIC, shell or c.

In-Process / embedded architectures

There are several embbedded technologies for web servers. Here the language interpretor is embedded into the web server, which makes it much faster, but it's more complex to use. Examples include ASP (where you can use one of several languages, e.g. Visual BASIC or Perl), and some with only one language, e.g. PHP/PHP, JSP/Java, mod_Perl/Perl.

Perl

Perl is a high-level language which is fast to develop in, and can run as a CGI script on a wide range of web servers and a wide range of operating systems. It can also be made to run much faster by using ASP or the mod_Perl interface. The CPAN library of pre-written code contains code to do most things you could think off - no other language has anything on this scale...

Returning to your questions. CGI/Perl is not the fastest way of doing things, but it's pretty good for low to medium volumes. If you have written the code well, it can probably be converted from CGI to mod_Perl, in which case it will run much faster.

There are many advantages of using a DB for storing data, and it should be easy to export data using Perl into any simple output fromat. Proper database systems have all the advantages of file-locking, multi-user capability, and potentially higher speeds. Examples include: MySQL, PostgreSQL or even DBD::SQLite all should be easy to use from Perl.

A basic Linux/Apache/Perl box with a 1GHz+ processor and 1Gb RAM, will run very quickly, and be adequate for most needs, but cost more than USD15/month. You may find that at your suggested price range your options are more limited.

One word of caution, you say you are a novice, in which case I would urge extreme caution if you are going to be moving money about. Web security is easy to get wrong, and you may be better off using code that someone else has written, and has been scrutinised by the public in general. I don't claim to know of such software.

Additional links to read:

• Is it Secure?
• (OT) Security Rant
• Shopping Cart
• Building a Large-scale E-commerce Site with Apache and mod_perl